Defect Detection and Identification in Si3N4 and SiC Using Controlled Reluctance Electromagnetic Test Methods

摘要

This test studied the feasibility of defect detection in Si3N4 and SiC using high frequency (32 MHz) electromagnetic techniques and focused field CREG test probes. Examined were test specimens which contained near surface defects - hardness indentation induced cracks, scratches, pits, and inclusions. While unable to detect cracks in the test pieces, it successfully demonstrated the ability to detect certain other defects - 19 microns high scratches in SiC, for example. Also observed were variations in electromagnetic signals which seemed to reflect variations in electrical and dielectrical properties of the test pieces, possibly due to variation in specimen microstructures and/or chemistry.